Process of making projecting screens



Dec. 20, 1932. T. SUZUKI 1,891,849

PROCESS OF MAKING PROJEQTINC- SCREENS I Original Filed Feb. 6, 1928 INVENTOR.' T 516 u Kl Patented Dec. 20, 1932 UNITED STATES PATENT OFFICETSUNEO SUZUKI, OF TOKYO, JAPAN, ASSIGNOR TO ZAIDAN HOJTN RIlZKAGAK'UKEN'KYUJO, OF TOKYO, JAPAN PROCESS OF MAKING PROJECTING SCREENS Originalapplication filed February 6, 1928, Serial No. 252,356, and in JapanMarch 31, 1927. Divided and this application filed. July 2, 1930. SerialNo. 465,403.

The present invention relates to the manufacture of projecting orlight-reflecting screens. This process consists in arranging lamellar orscaly crystals evenly and uniformly on a light-absorbing surface.

This application is a' division of application Serial No. 252,356, filedFeb. 6, 1928.

The object of the invention is to manufacture a new film. surface havinga property characterized by showing the phenomenon of diffuse reflectiononlyto directions which are limited within a conical surface having thedirectionof reflected ray, corresponding to the incident ray, referredto the film surface as an optical surface, as the axis and subtending acertain angle with it. When this film surface is applied, for example,to refleet a projected picture, it is able to show the picture withoutbeing influenced by the presence of other lights coming from directionscomparatively distant from that of the projecting apparatus.

The accompanying, drawing illustrates the action of diffuse reflectionmade by the new film surface according to the invention.

In the figure, let AB be a film surface having black, brown, dark blue,or dark violet colors, etc., absorbing much light, on which lamellar orscaly crystals are made to adhere evenly and uniformly arranged. Then abeam'of. light (very narrow bundle of light) is projected from a lightsource C to a point D on the film surface AB. Now, if the surface AB bean optical surface, that is. a mirror, the beam of light will bereflected in the direction DE, but in the case of the above stated filmsurface, the beam oflight is reflected diffusely to several directionslimited by an approximately conical surface containing DF and DG. If theeyes are brought to any point Within this cone, they will see a lightspot at D. I

The property like this, to make diffuse reflection in a limited space,can also be observed in more or less degree in the case of a metallicsurface provided with small convex and concave dots, 'as the mattsurface of metals. The inventor discovered that dark surfaces coveredwith lamellar or scaly crystals evenly and uniformly arranged have thesame property in a very marked degree.

When a beam of light is reflected by this film surface, the brightnessof the spot at D is maximum when it is viewed on the line DE, anddecreases gradually when the position of eye shifts towards F or G andat last nothing more can be seen.

The an les subtended by DE and DG or DE and DF are different accordingto the definition of what visible is, but practically the limit ofvisibility, referring to a certain light source, without much troublingthe eyes can be easily controlled from 10 degrees to 40 degrees bychanging the quantity of crys tals applied on the surface. For the sakeof convenience, let us call that angle EDF (or conical surfacecontaining the lines DG and DF the cone of diffuse reflection.

Now, assuming that a bundle of light from C having a larger angle isprojected upon the film surface AB, let CD be the central ray of thatbundle, and let DE be the path of the reflected central ray if thesurface AB be a mirror. Now the eye is brought on the line DE and thesurface AB is viewed. All rays coming from their light source C makediffuse reflection each in its cone of diffuse reflection; and as aresult an ellipse is seen on the surface, the brightness of which beinga. maximum at the central part of the ellipse, and decreasing towardsthe brim. The visual angle of the major diameter of that ellipse issmaller than the double of theangle of diffuse reflection. In the sameway, many bundles of light having larger angles from many light sourcesother than C, are made to project, at the same time, upon the filmsurface AB. Then the eye can see many ellipses at different parts ofthis surface; and the centers of these ellipses do notfall at} the samepoint. If the light sources are far enough apart, or the angle ofdiffuse reflection is small enough, the eye can see these ellipses asnot overlapping each other.

Now a bundle of light is projected upon this film surface by using anyprojecting apparatus, and the image is focussed upon 1t. Then this imagecan be seen clearly when the EDG) the angle of diffuse reflection, andthe time from directions quite apart from that of pro ectmg apparatus,many ellipses appear at different places on the surface, and

they will not overlap the image from the project ng apparatus. If thesize of the surface is limited to that which is only necessary forprojecting the image, and using a film surface whose angle of diffusereflection is well controlled, it is practically possible to show theimage in the presence of many light sources besides the projectingapparatus,

such as electric lamps, window light, and even 1n a very brightlylighted room without any influence upon the image.

With a film surface having an angle of diffuse reflection small enough,it is possible to project a picture even out-doors in the day time.

In the following example, the process of making the new film surface isexplained z A dark colored plate such as colored glass plate is coveredwith a thin layer of gelatine by any known method. Next, crystals suchas ammonium manganous phosphate or ammonium cobaltous phosphate, ortheir mixed crystals, obtained by suitable method are suspended in waterin a vat. Then the water 1n the vat is well agitated, the prepared plateis sunk down in it quickly before the susended crystals begin to settleto the bottom. o prevent the rotatory and wave motions =of water whichcause the crystals to heap at certain places during the precipitation,thus disturbing their even and uniform propagation over the surface ofplate, a rough grid made of wood or metal is sunk down into the watertaking care not to touch the plate. As soon as t rotatory and wavemotions of water are ubsided, the grid is slowly taken away, and thecrystals are allowed to precipitate upon the plate. After they are allprecipitated, the supernatant water is removed by means of siphon orother suitable arrangements quite slowly not disturbing the crystals inthe least. It is better to give a little inclination to the plate, asthen the draining off of the water takes place more easily and quickly.In this way, a film surface, a surface covered with lamellar or scalycrystals evenly and uniformly arranged, can easily be produced. Afterdraining off all the water, on drying, the crystals will stick to theplate by the action of the gelatine. Further to prevent the mechanicalwearing of the surface it is coated with any transparent varnishes,lacs, collodion, gelatine or gums. To harden the gelatine coating,formalin or chromium compounds may also be -used.

The manganous and cobaltous ammonium phosphates mentioned above are bothlamel- ,Ladenburgs Handworterbuch der Chemie.

see page 597, (1877), Breslay.-

The film surface made in this way looks dark or black, if it is viewedrightly with dark background (the back of one who looks at the surfacebeing dark). If an image is projected upon it, it can be seen veryclearly even in presence of'wmdows or electric lamps not too near to therojecting apparatus. Such presence of ot er light sources than theprojecting apparatus exerts least mfluence upon the image by the reasonwhich has hitherto been stated. On using the quantity of ammoniummanganous phosphate obtained from 3 to 4 grams of crystallized man'-ganous sulphate, per square meter of the film surface, the angle ofdlfiuse reflection amounts to about 10 degrees; that from 20 grams ofcrystallized manganous sulphate per square meter will give a filmsurface having the angle of diffuse reflection of about 30 de ees.

nstead of dark colored lass plate, ordinar glass plate can be use which18 coated with atine containing pigments such as lamp lack, anilineblack, Prusslan blue, Turnbulls blue, or ultramarine, or some colloidalcoloring matters as mgrosine, thus changing the surface of it muchabsorptive to the light. If the quantity of the pigments 105 of coloringmatters is controlled so as to give semi-transparent gelatine coating,the finished plate will give a fascinating image when it is projectedupon the film s1de, and properly illuminated at theback s 1de. The shadeof the image shows beautiful dark tints according to the pigments orcolormg matters used. Such a plate can be used for window pane and whenprojected upon 1t, the charming picture is enough to please theattendants.

Instead of gelatine, glue, casein, starch paste, gums, and agar-agar canused; and instead of glass plate, any metallic plates, or wooden platesoaked with any water-proofing material may be used. Further stufisexpanded on a frame, soaked with lac or rub ber solution so as to makeit more smooth and water proof, can also be used.

To make the crystals-adhere evenly and 125 uniformly arranged upon asurface, the pre cipitation from water as described just now, is thebest method. But carefully painting the crystals mixed with'suitablepaste, or printing with an ink contammg the crystals,

or blowingv the crystals upon the pasted surface will all give tolerablygood result.

Besides the crystals of ammonium manganous phosphate and ammoniumcobaltous phosphate, othencrystals such as mica, stannic sulphide, orany other lamellar or scaly crystals which are permanent in the air canalso be used with pretty good result.

On using this film surface for projection 10 of magic lantern orcinematographic pictures, there is no necessity of using dark rooms, orselecting night time. The projection can easily be made in day lighteven in out-door places, and at night in a place where stronglyilluminated by lamps, thus making a new epoch in disciplinal andeducational sense.

On using this film surface for projection,

the images from projecting apparatus'can be used as decorations in orout of the room.

What I claim is:

1. A process of making projecting screens comprising the steps of firstsuspending lamellar crystals in water, then immersing a coated platetherein and maintaining the suspension immobile, then removing thesupernatant water, and finally finishing the surface of the plate.

2. A process of making projecting screens so comprising the steps offirst suspending lamellar crystals in water, then coating a plate withgelatine, thereupon immersing the gelatine-coated plate in thesuspension while maintaining the suspension free from bodily motion,next allowing the crystals to settle upon said plate, then removingsupernatant water, drying the plate, and finally covering the plate witha coating.

In testimony whereof I affix n1 signature. 40 TSUNEO UZUKI.

